Method of preventing slag surge in thermite welding practice



- May 29,1928. 1,671,413

' D. C. DICKSON METHOD OF PREVENTING SLAG S URGE IN THERMITE WELDING PRACTICE Fila Sept. 1, 1925 uoentoro Patented May 29, 1928.

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THERMIT oonronn'rron, or cnarnanr, new resent, A coaronerron or-nnw I JERSEY.

METHOD OF PREVENTING SLAG SURGE IN THERMITE -WELDING PRACTICE.

Application filed September 1, 1925. Serial No, 53,9f18.

The invention relates to a novel method of preventing the surging of the slag within the mold in thermite welding practice, in

which the elements to be welded by the molten thermite metal are enclosedin a mold and the superheated molten thermite metal is teemecl into the mold from a crucible located above the same, the method comprising the teeming of substantially all of the molten metal directly into the pouring gate of the mold and then diverting the portion of the molten stream containing the slag from the gate entrance by relative lateral movement of the crucible and mold, so that the falling slag stream will not impact the molten metal within the mold.

The operation of the invention is illustrated in the accompanying drawings, in which: i i

Fig. l is a sectional elevation of a mold with the crucible in its initial pouring position relative to the pouring gate.

Fig. 2 is a similar view showing the final position of the crucible.

Referring to the drawings, 1 indicates a typical mold, having a preformed cavity 2 into which the ends of the rails to be welded extend, the cavity receiving the superheated 'molten metal discharged from the bottom of crucible 4, which is directed into said cavity by a pouring gate 3.

In alumino-thermic welding, more particularly in welding the ends of rails, effected by tapping highly heated thermite metal, such as steel, from a crucible, into a mold containing the parts to be welded, it has been found 7 that the highly molten slag, which floats on the molten steel in the crucible, frequently gains access to the interior of the mold and comes in contact with the surfaces to be welded, resulting in weakened and imperfect welds due to the adhesion of the slag to the metal. It has been found that the entranceof the slag into the mold cavity is due to the surge set up by 'thefalling stream of molten slag into the mold cavity, after the thermite steel has entered and substantially filled the mold. It has been proposed heretofore to prevent this surging of the slag by pouring the molten stream containing the slag upon an angularly disposed wall of the pouring gate to dissipate the force the small top surface of the mold contains numerous'gates, risers and vent holes, leaving little or no room for the provision of an inclined pouring surface adjacent the upper portion of the pouring gate. Furthermore, in the use of such small quantities of thermite as is employed in rail welding, it frequently happensthat the molten stream does not fall exactly vertically downward and it ,is more or less diflicult to direct the stream onto any particular partof the mold, with any great accuracy. Inorder to avoid these'difliculties, and nevertheless to ovcrcome'the very objectionable slag surge and trapping within the mold, I have found it suflicient to deflect the falling stream of molten material from direct entrance into the pouring gate by had an opportunity to enter the pouring gate. This relative lateral movement of the crucible and mold need not be extensive, but should be sufficient to carry the falling stream of molten slag out of alignment with theentrance to the pouring gateand preferably into a position vertically above the top surface of the mold, which is not pierced by any of the various openings. The preferred procedure, because of the lightness of the crucible and because, in rail-welding practice, it is usual to mount the crucible on a swinging arm, is to move the crucible aside slightly relatively to the mold just 'as the last portions of the molten steel are being discharged from the crucible, so that the 1. The method of preventing slag surging in thermite welding practice which comprises deflecting the molten stream from the pouring gate of the mold approximately with the discharge of the final portion of the steel from the crucible.

2. The method of preventing slag surging in thermite Welding practice which comprises teeming the molten metal vdirectly into the gate entrance by relative lateral movement of the crucible and the mold.

In testimony whereof I a'HiX my signature.

DONALD CAMERON nIcKsoN. 

